AC Electroluminescent Processes in Pr-Activated (BaCa)TiO₃ Diphase Polycrystals.

We investigated the properties of alternating current (AC)-driven electroluminescence from (BaCa)TiO₃:Pr diphase polycrystal-based device. The results of crystal phases and micrographs, and the symmetrical dual emissions in one AC cycle, indicate the spontaneous formation of a dielectric/phosphor/dielectric sandwich microstructure in (BaCa)TiO₃:Pr. The electroluminescent device emits a red light of 617 nm, which is attributed to the ¹D₂-³H₄ transition of Pr in the phosphor phase. At a fixed AC frequency, the intensity of electroluminescence exhibits a steep enhancement when applying an increased driving electric field that is beyond a threshold. In a fixed driving electric field, the intensity of electroluminescence shows a rapid rise at low frequencies, but reaches saturation at high frequencies. Based on a double-injection model, we discussed systematically the electroluminescent processes in a whole cycle of AC electric field, which matched well with the experimental data. Our investigation is expected to expand our understanding of such a diphase electroluminescent device, thereby promoting their applications in lighting and displays.